Apocalypse When? No Certainty of a Milky Way -- Andromeda Collision

TL;DR

This study uses recent astronomical data to explore the future interactions between the Milky Way and Andromeda galaxies, revealing significant uncertainties that could lead to different collision scenarios or no collision at all within 10 billion years.

Contribution

It provides a comprehensive analysis of the future evolution of the Local Group considering multiple galaxies and their uncertainties, challenging the assumption of an inevitable collision.

Findings

Uncertainties in galaxy positions and masses greatly affect collision predictions.

Including M33 increases the likelihood of a merger.

The Large Magellanic Cloud's orbit reduces the merger probability.

Abstract

It is commonly believed that our own Milky Way is on a collision course with the neighbouring Andromeda galaxy. As a result of their merger, predicted in around five billion years, the two large spiral galaxies that define the present Local Group would form a new elliptical galaxy. Here we consider the latest and most accurate observations by the Gaia and Hubble space telescopes, along with recent consensus mass estimates to derive possible future scenarios and identify the major sources of uncertainty in the evolution of the Local Group over the next 10 billion years. We find that the next most massive Local Group member galaxies -- namely, M33 and the Large Magellanic Cloud -- distinctly and radically affect the Milky Way - Andromeda orbit. While including M33 increases the merger probability, the orbit of the Large Magellanic Cloud runs perpendicular to the Milky Way - Andromeda orbit and makes their merger less likely. In the full system, we find that uncertainties in the present positions, motions, and masses of all galaxies leave room for drastically different outcomes, and a probability of close to 50% that there is no Milky Way - Andromeda merger during the next 10 billion years.